Add a glow effect around the Earth
Disclaimer: I just learned this myself, so @NoviceInDisguise can edit it if needed.

1

Create a bright point of light in your scene. This would be planet earth- already created in your case. Glare can't happen without a target.

Render the image.



2

At the top of your screen, change the screen layout mode to be compositing. Once done, you may need to check a little box in the node editor that says use nodes.



3

Add a glare filter between the image input and the finished output. Optionally you may add a viewer node at the end of the string so you can see the image in the node editor. In order for a viewer node to be active, you need to check Backdrop. It's located near use nodes.

Set the glare mode to fog glow.



4

Mess with the settings on the glare node until you have a perfectly glowing planet.